Complementary metal-oxide-semiconductor (CMOS) technology is the dominant semiconductor technology used for the manufacture of ultra-large scale integrated (ULSI) circuits today. Size reduction of the semiconductor structures has provided significant improvement in the speed, performance, circuit density, and cost per unit function of semiconductor chips over the past few decades. Significant challenges, however, are faced as the sizes of CMOS devices continue to decrease.
One such challenge is the fabrication of interconnect structures, e.g., vias. CMOS devices typically include semiconductor structures, such as transistors, capacitors, resistors, and the like, formed on a substrate. One or more conductive layers formed of a metal or metal alloy separated by layers of a dielectric material are formed over the semiconductor structures to interconnect the semiconductor structures and to provide external contacts to the semiconductor structures. Vias are formed in the dielectric layers to provide an electrical connection between metal layers and/or a metal layer and a semiconductor structure.
The vias, particularly vias connecting a metal lead with a thin metal line to an underlying conductive layer, are frequently subjected to significant stress. The stress may result from, for example, the different coefficient of thermal expansion (CTE) between the material filling the via and the surrounding material, e.g., the dielectric layer. The stress frequently causes voids, commonly referred to as stress-induced voids (SIV), wherein the material filling the void separates from the underlying conductive material. The stressed-induced voids may significantly affect the electrical characteristics of the via and may cause the semiconductor structure to fail. Therefore, there is a need for a semiconductor structure that eliminates or reduces the amount of stress, and therefore the stressed-induced voids, in vias.